Within the wind power industry, it is common to utilize bearing systems for the wind turbine main shafts which are configured to handle large radial loads as well as large angular misalignments between a rotating shaft and the supporting bearing axis. These main shaft bearing systems typically comprise spherical roller bearings (SRBs) having separate rotating seal carriers and a locating bearing locknut device to secure the rotating seal carriers and the spherical roller bearing inner race against a main shaft shoulder. The cylindrical outer diameter of the outer race of the spherical roller bearing is secured into a cylindrical inner diameter of a pillow block housing with an axial clamp end cover plate. The internal configurations of spherical roller bearing systems have the ability to carry large radial loads and to accommodate large dynamic and static angular misalignments, as well as modest axial loads, without generating overturning moment reactions in the pillow block housing and supporting bedplate structures. Additionally, these bearing systems require no bearing setting setup procedure, making them easy to install in practice.
However, spherical roller bearing systems have inherent problems. In particular, the spherical roller bearings must operate with a generous radial internal clearance (RIC). In a wind turbine main shaft application, dynamically variable wind loads placed on the spherical roller bearing during operation cause large axial and radial deflections within the spherical roller bearing system as a result of the large radial internal clearance. These deflections dramatically reduce spherical roller bearing life in an unpredictable manner due to a loss of load sharing to the rotor side roller row and wind vibration induced peeling and/or false brinelling of the raceway surfaces, which initiates premature raceway spalling. The deflections further reduce bearing life of a downstream gearbox input shaft support due to excessive axial shaft deflection, which in turn leads to excessive thrust loads.
The large radial internal clearance of the spherical roller bearing systems and the inherent angular degree of freedom of the outer race with respect to the inner race further requires associated axial and radial labyrinth seal gap clearances to be large enough to prevent metal-to-metal contact within the labyrinth gap between the rotating seal carrier labyrinth rings and the stationary labyrinth end covers. This large gap clearance reduces the effectiveness of the labyrinth seal in preventing lubricant loss and contaminant exclusion. Similarly, the rotating shaft seal, typically a polymer v-ring face seal, must be able to accommodate the large dynamic angular, radial, and axial motions in addition to the normal shaft rotational movement.
To gain access to the gearbox end roller row, spherical roller bearing systems typically require a loosening and sliding back of the bearing locknut and press fit rotating seal carrier labyrinth ring, which makes in-service inspection of the bearing raceway and roller surfaces on the gearbox end of the pillow block bearing difficult. Furthermore, no access is available to the rotor end roller row, because the rotor end stationary labyrinth seal end cover is trapped by the rotating seal carrier labyrinth ring, which cannot be removed unless the main shaft is withdrawn from the spherical roller bearing system, a very difficult or impossible task within the application environment of an operating wind turbine.
Accordingly, there is a need for a wind turbine main shaft support bearing system which is capable of carrying the expected application loads experienced in the wind turbine operational environment, which does not require large radial internal clearances associated with the supporting roller elements and hence has a predictable operational life, and which does not require large axial and radial labyrinth seal gap clearances to prevent metal-to-metal contact within the labyrinth gap between the rotating seal carrier labyrinth rings and the stationary labyrinth end covers.
Additionally, there is a need for a wind turbine main shaft support bearing system which does not require a loosening and sliding back of the bearing locknut and press fit rotating seal carrier labyrinth ring to enable in-service inspection of the gearbox end bearing raceway and roller surfaces, and which provides a means to access the rotor end roller row.